The present invention relates to a method of manufacturing semiconductor devices. More particularly the invention relates to a method of covering and protecting a semiconductor chip.
In recent years, resin in the interrelated group of polyimide, hereinafter referred to as polyimide resin has been watched because of its heat resisting nature and utilized in various ways in the manufacture of semiconductor devices. The latest trend is to use polyimide resin even as a covering and protecting film. Its use is for the purpose of protecting the surfaces of semiconductor devices from scratches or damages during or after manufacture thereof. In addition, it has become known that polyimide resin also has the effect of preventing "soft errors" of a semiconductor chip.
By the term "soft errors" is meant extremely vexatious troubles wherein .alpha.-rays are radiated by radioactive substance contained in the material of an encapsulating package in the order of PPM, or parts per million, resulting in the destruction of memory data.
However, polyimide resin performs poorly in adhesiveness, more so in regard to a film of oxidized silicon. Polyimide resin thus has a weakness that its sealing effect is not sufficient. Because of this, according to the current practice, polyimide resin is coated thin, so that the thickness of its film is approximately 1 .mu.m, then heat treated and hardened until the film adheres closely. Thereafter, polyimide resin is applied again, so that its film thickness is approximately 20 .mu.m, for example, then heat treated and hardened. In spite of this, its adhesiveness is not satisfactorily improved.
An object of the invention is to eliminate the defects of the prior and conventional art and to provide a method of manufacture which improves adhesiveness of a surface protection film consisting of a thermosetting resin, especially polyimide resin.